1. Field of the Invention
The present invention relates to a multilayer structure useful for electrical insulation.
2. Description of the Related Art
Kraft paper, made from cellulose pulp, is widely used as a solid electrical insulation in oil filled transformers because of its good insulating properties and economy. However, the cellulose polymer is susceptible to hydrolysis from long term exposure to high temperatures. Thermal stability as well as mechanical strength can be improved by blending high temperature synthetic fibers with the cellulose pulp. A polymer binder is added to facilitate bonding between the synthetic fibers and the cellulose pulp. However, the polymer binder can cause non-uniformity in the paper and sticking problems during paper processing and its usage in contact with transformer coils during high temperature operations.
It is therefore desirable to prepare a paper for electrical insulation with improved thermal stability and mechanical strength while reducing its sticking in processing and the final end-use.